This invention relates to the casting of metal strip by continuous casting in a twin roll caster.
In a twin roll caster, molten metal is introduced between a pair of counter-rotated horizontal casting rolls that are cooled so that metal shells solidify on the moving casting roll surfaces and are brought together at a nip between them to produce a solidified strip product delivered downwardly from the nip between the casting rolls. The term “nip” is used herein to refer to the general region at which the casting rolls are closest together. The molten metal may be poured from a ladle into a smaller vessel or series of smaller vessels from which it flows through a metal delivery nozzle and nozzles located above the nip forming a casting pool of molten metal supported on the casting surfaces of the casting rolls immediately above the nip and extending along the length of the nip. This casting pool is usually confined between side plates or dams held in sliding engagement with end surfaces of the casting rolls so as to restrict the two ends of the casting pool against outflow.
The twin roll caster is capable of continuously producing cast strip from molten steel through a sequence of ladles positioned on a turret. The molten metal is poured from each ladle in turn into a tundish and then into a moveable tundish before flowing through the metal delivery nozzle into the casting pool. The tundish enables the exchange of an empty ladle for a full ladle on the turret without disrupting the production of the cast strip.
In casting thin metal strips, it is often important to control the edge thickness of the thin metal strip during the casting process. For example, it is not uncommon in certain instances for the portion of the thickness of the strip in close proximity to a side edge of the thin strip to be too thin or wavy. It is additionally important to control the thickness profile to ensure that the strip is not too thick or thin. Therefore, there is a need to better control the thickness of the thin strip at and/or in close proximity to the strip side edges and even more generally across the strip width. There is also a need to provide automated control, as manual control may result in delayed responses to undesired changes in strip thickness, which in turn impacts product quality.